Certain tightening devices aim to cause the forward portion of the foot to act as much as possible as a unit with the shell, particularly in the transverse direction, while at the same time avoiding excessive local contact pressures which interfere with the blood circulation and are the cause of sensations of cold, smarting or other pains, comprising a strap whose lower end is solid with the lower part of the shell and whose upper end is solid with a screw-nut device adjustable and controllable by the user. This strap surrounds the upper part of the forward portion of the foot in the metatarsal region, while being generally supported, with or without the interposition of a force distribution plate, on a soft slipper covering the foot. As to the desired technical effect, these devices generally give satisfaction, obviously to different extents depending on the case.
It has however been confirmed that often the known devices do not really assure comfortable retention and good envelopment of the foot. Finally, if the user is led to withdraw the slipper from the shell for any reason whatever, such as repair, drying, etc., the interior portion of the device very often tends to collapse downwardly and thus to restrict the space which remains free, which interferes with its replacement.